1. Field of the Invention
The present invention relates to an electric connection technique of electronic parts and, more particularly, to a minute contact piece for making electrical conduction by contacting an electrode of a semiconductor device represented by an LSI and a contact piece member used for such a contact piece.
2. Description of the Related Art
In recent years, with the demand for high performance and miniaturization of electronic equipments, there also is a demand for high performance and miniaturization of semiconductor devices, such as an LSI to be mounted on an electronic equipment. Accordingly, it is required for the semiconductor device concerned to miniaturize wiring patterns and make a wafer thinner so as to integrate more circuits into a smaller volume.
Moreover, a higher speed operation is demanded, and the wiring patterns of the semiconductor device are miniaturized, and a reduction in wirings between circuits is attempted. Further, since more functions/circuits are integrated into a single semiconductor device, a number of terminals provided in the semiconductor device concerned is also increasing.
In such a situation, in order to perform a test for the semiconductor device concerned, a so-called contactor having contact pieces capable of stably contacting with many minute terminals is demanded.
If classified according to contact pieces used, contactors for an LSI test is classified into four kinds, that is, 1) a probe-type contactor, 2) a contactor using spring probes as contact pieces, 3) a contactor using a membrane probe as contact pieces, and 4) a contactor using an anisotropic conductive rubber as contact pieces.
1) Contactor of a Needle Type
Formed by arranging individual needles (needles formed of tungsten wire or the like) on a contactor substrate so as to match terminal positions of an LSI to be tested.
1-a) Cantilever System:
It is configured so that the needles extend in an inclined state from above to electrodes of a semiconductor device.
1-b) Perpendicular Needle System:
Conductive and perpendicularly standing needles (bar-like members) are used as contact pieces.
1-c) Bent Needle System:
Contactor using contact pieces having elasticity by bending a middle of conductive and perpendicularly standing needles.
2) Contactor Using Spring Probes as Contact Pieces
A probe pin is configured to have contact part to be contacted with a terminal of a semiconductor device and a contact part to be contacted with a substrate and a spring is arranged between the contact parts. An electric contact is acquired by pressing the contact parts onto the terminal of the semiconductor device and the substrate for test by elasticity of the spring between the contact parts.
3) Contactor Using a Membrane Probe as Contact Pieces
The membrane probe is formed as a film-like circuit board having metal protrusions as contact piece electrodes for probes.
4) Contactor Using an Anisotropic Conductive Rubber
The anisotropic conductive rubber is formed by using a rubber as an insulating material and embedding therein a material (metal wire or the like) which is conductive in only a direction of a thickness.
In any of the above-mentioned methods, pressurization of about 0.05 N (5 gf)−0.1 N (10 gf) is performed so as to stabilize and reduce an electric contact resistance.
The contact resistance is a sum of a film resistance, a constriction resistance and a resistance of a contact piece. The reason for a decrease in a contact resistance by pressurization is especially due to that the constriction resistance can be reduced.
Since minute unevenness exists in a surface of each of the contact piece and a terminal of an electronic part and an electric connection is performed by only the minute protrusions on the surfaces of the both, the substantial contact area is reduced and a high constriction resistance is generated.
As shown in FIG. 1, a surface 4a of a terminal 4 for LSI test on a semiconductor chip 2 has irregularity when viewed microscopically. FIG. 2 is an illustration showing a state where a needle type contact piece 6 is brought into contact with the test terminal 4. The terminal surface 4a has unevenness as shown in FIG. 1, and when the needle type contact piece 6 is brought into contact with that, parts of the contact piece 6 and the surface 4a of the terminal 4 which are truly in contact are only a part. Accordingly, the constriction resistance at the contact part is large. The sum of the constriction resistance and the film resistance by a film on the contact piece surface is a contact resistance, and, thus, the contact resistance is high if the constriction resistance is high. For this reason, the contact area of the contact piece and the electronic part is increased by applying a large pressure between the both, thereby reducing the contact resistance.
Moreover, as a contact method other than the above-mentioned contactor, the following Patent Document 1 discloses a method of producing a hole for a contract electrode on a silicon substrate by using a silicon processing technique so as to locate the contact piece in the hole. Here, it is suggested to use a spherical or ring-like elastic material of which surface is given an electric conductivity.
Patent Document 1: Japanese Laid-Open Patent Application No. 2002-5992
From the demand for semiconductor devices such as an LSI, there are required the following functions.
A) Making minute terminals: A contactor having contact pieces with small intervals which can contact with minute terminals.
B) Making low-voltage: A contactor of which pressure when contacting is low and a contact resistance is in a stable and low state so as to reduce influences, when contacting, with respect to thinning of wafers.
As mentioned above, reduction of contact resistance is based on reduction of the constriction resistance due to expansion of a contact area. Generally, pressurization is made with a contact pressure of 0.05 N (5 gf)−0.1 N (10 gf) per one pin, and when calculating a sum with respect ten thousands terminals, it reaches up to 50 N-100 N, which gives a very large influence such as causing destruction of a semiconductor device to be tested.
C) Making area free: Contact piece electrodes can be arranged not only in a peripheral area but also in a lattice-like from. With increase in a number of terminals, there is a need to contact with not only terminals arranged in edge portions of a semiconductor chip but also terminals arranged in a lattice-like form on the semiconductor chip.
D) Making wide area: Contact pieces capable of contacting with a plurality of LSIs collectively.
As for the functions required, features in each structure/method of the above-mentioned contactors are as follows.
1) Contactor of a Needle System
1-a) Cantilever Method:
Terminal intervals on a substrate side are larger than terminal intervals on a wafer side, which provides a restriction in terminal arrangement on a structure and cannot be dealt with the above-mentioned issue C. Additionally, there is a large restriction with respect to the issue D. Accordingly, there is a problem in that, for example, terminals cannot be arranged in an area array state or contact cannot be made simultaneously with adjacent semiconductor chips since a probe size is larger than a chip size.
1-b) Perpendicular Needle System:
With respect to the issue A, the displacement is in a buckling mode, and a direction of needle bending cannot be specified. For this reason, there is a possibility that adjacent pins contact and detangle with each other. Additionally, with respect to issue B, it is difficult to acquire a stable contact at a low-pressure.
1-c) Bent Needle System:
Although it depends on a degree of bending, in order to arrange with a small pitch, adjacent needles (pins) become obstacles. Additionally, in the structure in which needles are bent one after another, a manufacturing cost is very high.
2) Contactor Using a Spring Probe (POGO-PIN) as a Contact Piece
There are Many Component Parts Such as a spring, a contact part and a barrel part accommodating the spring, and there is a limitation structurally in narrowing pitch. With respect to the issue A, there is a limitation structurally in narrowing pitch. That is, there is a limitation in reducing a winding diameter of the coil spring.
Moreover, with respect to the issue B, since there is no wiping action which can break an oxide film of an LSI terminal, a stable contact cannot be obtained at a low pressure. Additionally, in order to maintain positioning accuracy of a needle end, there is needed separately a part having holes processed with high accuracy
3) Contactor Using a Membrane Probe as a Contact Piece
With respect to the issue A, since the contact electrodes are coupled by an insulating substrate, the individual electrode cannot move freely at a narrow pitch. Since a movable range of the contact electrode is small and it is a metal bump, it lacks flexibility. Thus, there is a problem in that a contact defect of a low bump is caused due to variation in heights of adjacent bumps.
On the other hand, with respect to the issue D, since wirings extend as threading between contact electrodes, there is a limitation in a number of wirings. Further, wirings of a membrane system do not progress in making multi-layered, and it is an extent in that wirings are provided on both sides of an insulating substrate. With respect to the issue B, it is difficult to obtain a stable contact since deformation cannot be made if there is no pressure of a certain degree.
4) Contactor Using an Anisotropic Conductive Rubber as a Contact Piece
With respect to the issue A, it cannot deal with narrowing pitch. Additionally, there are other problems such that a heat resistance is low, a durability is low or the like.
Moreover, although a contact electrode can be produced with narrow pitch according to the method disclosed in the above-mentioned Patent Document 1, it is difficult to form the rubber stably with a minute shape. Additionally, it is further difficult to form a metal or conductive film around the rubber. Further, if a conductive film can be formed, the durability thereof will be a problem.
As mentioned above, according to the contact pieces of the conventional technology, it is not possible to provide a contactor, which solves all issues such as A) making minute terminals, B) making a low pressure, C) making a wide area and D) making area free, and has durability in a minute size.